Did you get them used? Another thing you might have to check is if the shock is the right length for the ammount you lowered the spring in the rear... If this is not adjusted properly, you WILL have a sh!tty feeling ride...

In other words, if you lower the car at the springs in the rear, you must shorten the legnth of the shock and vice versa when raising it...

I learned this the hard way, when I had a set of function&form type2's(OEM style rear) on my 350z and then switched them over to my G35 sedan... I adjusted the rear springs but left the shocks the same legnth, and boy was I bouncing around like a lowrider on the freeway...